Optical systems

ABSTRACT

Optical systems that may, for example, be used in light ranging and detection (LiDAR) applications, for example in systems that implement combining laser pulse transmission in LiDAR and that include dual transmit and receive systems. Receiver components of a dual receiver system in LiDAR applications may include a medium range (50 meters or less) receiver optical system with a medium entrance pupil and small F-number and with a medium to wide field of view. The optical system may utilize optical filters, scanning mirrors, and a nominal one-dimensional SPAD (or SPADs) to increase the probability of positive photon events.

PRIORITY INFORMATION

This application claims benefit of priority of U.S. ProvisionalApplication Ser. No. 62/378,104 entitled “OPTICAL SYSTEMS” filed Aug.22, 2016, the content of which is incorporated by reference herein inits entirety.

BACKGROUND

Remote sensing technologies provide different systems with informationabout the environment external to the system. Diverse technologicalapplications may rely upon remote sensing systems and devices tooperate. Moreover, as increasing numbers of systems seek to utilizegreater amounts of data to perform different tasks in dynamicenvironments; remote sensing provides environmental data that may beuseful decision-making. For example, control systems that direct theoperation of machinery may utilize remote sensing devices to detectobjects within a workspace. In some scenarios, laser based sensingtechnologies, such as light ranging and detection (LiDAR), can providehigh resolution environmental data, such as depth maps, which mayindicate the proximity of different objects to the LiDAR.

SUMMARY

Optical methods and systems are described herein that may, for example,be used in light ranging and detection (LiDAR) applications, for examplein systems that implement combining laser pulse transmission in LiDARand that include dual transmit and receive systems. Receiver componentsof a dual receiver system in LiDAR applications may include anembodiment of a medium range (e.g., 50 meters or less) receiver opticalsystem with a medium entrance pupil (e.g., within a range of 10 to 15millimeters (mm), for example 12.7 mm) and small F-number (e.g., 1.6 orless) and with a medium to wide field of view. (The entrance pupil isthe optical image of the physical aperture stop as seen through thefront of the optical system). In some embodiments, field of view of themedium-range optical system may be between 15 degrees and 60 degrees.The optical system may utilize optical filters, scanning mirrors, and anominal one-dimensional SPAD (or SPADs) to increase the probability ofpositive photon events.

An example light ranging and detecting (LiDAR) device is described thatcombines laser pulse transmissions in a common optical path and in whichembodiments of the optical systems as described herein may beimplemented. In the example LiDAR device, different laser transmittersmay transmit respective trains of pulses which may be combined andseparated in the common optical path of the LiDAR according to thepolarization state of the laser pulses. In this way different types oflaser pulses may be combined, including laser pulses with differentwavelengths, widths, or amplitudes. The transmission of laser pulses inthe different trains of pulses may be dynamically modified to adjust thetiming of when laser pulses are transmitted so that different scanningpatterns may be implemented. Receiver components of the LiDAR device mayincorporate embodiments of the medium range receiver optical system asdescribed herein. In various embodiments, receiver components of theLiDAR device may also incorporate embodiments of a long range (e.g., 20meters to 200 meters) and/or short range (e.g., 20 meters or less)receiver optical systems as described herein. An advantage of the dualtransmit and receive system for LiDAR is a realizable architecture thatincludes scanning mirrors, micro electro-mechanical (MEMS) mirrors,single photon-avalanche detectors (SPADs) for counting singlephotoelectron events from close (short) range (e.g., 20 meters or less),medium range (e.g., 50 meters or less), and/or long-range (e.g., 20meters to 200 meters) with acceptable manufacturing risk, eye safetymargin, and probability of photon detection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example embodiment of an optical system that may,for example, be used as a medium range receiver optical system in LiDARapplications.

FIG. 2 illustrates an example embodiment of an optical system that may,for example, be used as a long range receiver optical system in LiDARapplications.

FIG. 3 illustrates an example embodiment of an optical system that may,for example, be used as a short range receiver optical system in LiDARapplications.

FIG. 4 illustrates an example embodiment of an optical system that may,for example, be used as a short range receiver optical system in LiDARapplications.

FIG. 5 illustrates an example embodiment of an optical system that may,for example, be used as a long range receiver optical system in LiDARapplications.

FIG. 6 illustrates an example embodiment of an optical system that may,for example, be used as a short range receiver optical system in LiDARapplications.

FIGS. 7A and 7B are logical block diagrams of an example LiDAR systemthat combines laser pulse transmissions in light ranging and detecting(LiDAR), according to some embodiments.

FIGS. 8A and 8B illustrate an example optical path for laser pulses andpulse reflections, according to some embodiments.

FIG. 9 is a high-level flowchart of a method of operation for a LiDARsystem that includes light transmitters and receivers that includeoptical systems as illustrated in FIGS. 1 through 6.

This specification includes references to “one embodiment” or “anembodiment.” The appearances of the phrases “in one embodiment” or “inan embodiment” do not necessarily refer to the same embodiment.Particular features, structures, or characteristics may be combined inany suitable manner consistent with this disclosure.

“Comprising.” This term is open-ended. As used in the appended claims,this term does not foreclose additional structure or steps. Consider aclaim that recites: “An apparatus comprising one or more processor units. . . .” Such a claim does not foreclose the apparatus from includingadditional components (e.g., a network interface unit, graphicscircuitry, etc.).

“Configured To.” Various units, circuits, or other components may bedescribed or claimed as “configured to” perform a task or tasks. In suchcontexts, “configured to” is used to connote structure by indicatingthat the units/circuits/components include structure (e.g., circuitry)that performs those task or tasks during operation. As such, theunit/circuit/component can be said to be configured to perform the taskeven when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invoke 35U.S.C. § 112(f), for that unit/circuit/component. Additionally,“configured to” can include generic structure (e.g., generic circuitry)that is manipulated by software and/or firmware (e.g., an FPGA or ageneral-purpose processor executing software) to operate in manner thatis capable of performing the task(s) at issue. “Configure to” may alsoinclude adapting a manufacturing process (e.g., a semiconductorfabrication facility) to fabricate devices (e.g., integrated circuits)that are adapted to implement or perform one or more tasks.

“First,” “Second,” etc. As used herein, these terms are used as labelsfor nouns that they precede, and do not imply any type of ordering(e.g., spatial, temporal, logical, etc.). For example, a buffer circuitmay be described herein as performing write operations for “first” and“second” values. The terms “first” and “second” do not necessarily implythat the first value must be written before the second value.

“Based On.” As used herein, this term is used to describe one or morefactors that affect a determination. This term does not forecloseadditional factors that may affect a determination. That is, adetermination may be solely based on those factors or based, at least inpart, on those factors. Consider the phrase “determine A based on B.”While in this case, B is a factor that affects the determination of A,such a phrase does not foreclose the determination of A from also beingbased on C. In other instances, A may be determined based solely on B.

DETAILED DESCRIPTION

Optical methods and systems are described herein that may, for example,be used in remote sensing systems such as light ranging and detection(LiDAR) applications, for example in systems that implement combininglaser pulse transmission in LiDAR as illustrated in FIGS. 7A and 7B.LiDAR is a remote sensing technology that directs a laser or lasers at atarget and measures a distance to the target according to a reflectionof the laser(s) detected at the LiDAR. The distance may be calculatedbased on the difference between the time at which a laser pulsetransmission is sent and a time at which a reflection of the laser pulsetransmission is received. Distance measures calculated by LiDAR are usedin many different applications. For instance, multiple distance measurestaken over an area can be processed to generate a high resolution map,which can be used in a variety of different applications, including, butnot limited to, geological surveys, atmospheric measurements, objectdetection, autonomous navigation, or other remote environmental sensingapplications. Note that the term “LiDAR” as used herein is sometimesdesignated or referred to in other texts differently, including suchterms as “Lidar”, “lidar”, “LIDAR”, or “light radar.”

Medium-Range, Long-Range, and Short-Range Receiver Optics

FIGS. 1 through 6 and Tables 1A through 6 illustrate various embodimentsof optical systems that may, for example, be used as medium-range,long-range, and short-range optical systems in medium-range, long-range,and short-range receivers of remote sensing systems such as LiDARsystems, for example as illustrated in FIGS. 7A-7B and 8A-8B. Anadvantage of the dual transmit and receive system for LiDAR is arealizable architecture that includes scanning mirrors, microelectro-mechanical (MEMS) mirrors, single photon-avalanche detectors(SPADs) for counting single photoelectron events from close (short)range (e.g., 20 meters or less), medium range (e.g., 50 meters or less),and/or long-range (e.g., 20 meters to 200 meters) with acceptablemanufacturing risk, eye safety margin, and probability of photondetection.

Components of a dual receiver system in LiDAR applications may include arelatively small aperture, wide field of view optical system forshort-ranges (referred to as a short-range optical system), a mediumaperture, medium to wide field of view optical system for medium-ranges(referred to as a medium-range optical system), and/or a relativelylarge aperture optical system with a smaller field of view forlong-ranges (referred to as a long-range optical system). Theshort-range, medium-range, and long-range optical systems may utilizeoptical filters, scanning mirrors, and a sensor, for example one or moresingle photon-avalanche detectors (SPADs), to increase the probabilityof positive photon events.

In some embodiments, the dual receiver system may include two lighttransmitters (e.g., lasers) that transmit light through a common opticalpath to an object field, and two light receivers that detect reflectionsof the transmitted light received at the system through the commonoptical path. The light receivers may include a short-range opticalsystem including lens elements that refract a portion of the lightreflected from within a range of, for example, 20 meters or less to asensor configured to capture the light, a medium-range optical systemincluding lens elements that refract a portion of the light reflectedfrom within a range of, for example, 50 meters or less to a sensorconfigured to capture the light, and/or a long-range optical systemincluding one or more lens elements that refract a portion of the lightreflected from within a range of, for example, 20 meters or more to asensor configured to capture the light. In some embodiments, ashort-range optical system has a small aperture and provides a widefield of view, a medium-range optical system has a medium aperture thatprovides a medium to wide field of view, and a long-range optical systemhas a large aperture and provides a small field of view.

In some embodiments, the medium-range optical system may include fiverefractive lens elements. In some embodiments, field of view of themedium-range optical system may be between 15 degrees and 60 degrees. Insome embodiments, F-number of the medium-range optical system may be 1.6or less. In some embodiments, the surfaces of the lens elements in themedium-range optical system are one of spherical, even-aspheric, orflat/plano surfaces. In some embodiments, the medium-range opticalsystem may include an optical bandpass filter, or alternatively anoptical bandpass filter coating on a plano surface of one of the lenselements.

In some embodiments, the long-range optical system may include fiverefractive lens elements. In some embodiments, field of view of thelong-range optical system may be 15 degrees or less. In someembodiments, F-number of the long-range optical system may be 1.2 orless. In some embodiments, the surfaces of the lens elements in thelong-range optical system are one of spherical, even-aspheric, orflat/plano surfaces. In some embodiments, the long-range optical systemmay include an optical bandpass filter, or alternatively an opticalbandpass filter coating on a plano surface of one of the lens elements.

In some embodiments, the short-range optical system may include sevenrefractive lens elements. In some embodiments, the short-range opticalsystem may include six refractive lens elements. In some embodiments,the short-range optical system has a field of view of between 45 and 65degrees. In some embodiments, F-number of the short-range optical systemmay be 2.0 or less. In some embodiments, the surfaces of the lenselements in the short-range optical system are one of spherical,even-aspheric, or flat/plano surfaces. In some embodiments, theshort-range optical system may include an optical bandpass filter, oralternatively an optical bandpass filter coating on a flat/plano surfaceof one of the lens elements.

Note that the various parameters of the optical systems are given by wayof example and are not intended to be limiting. For example, the opticalsystems may include more or fewer lens elements than described in theexample embodiments, shapes of the lens elements may vary from thosedescribed, and the optical properties (e.g., field of view,aperture/entrance pupil, F-number, etc.) of the optical systems may bedifferent than those described while still providing similar performancefor the optical systems. Further note that the optical systems may bescaled up or down to provide larger or smaller implementations of theoptical systems as described herein.

While embodiments of optical systems are described in reference to usein systems such as LiDAR systems, the optical systems described hereinmay be used in a variety of other applications. Also note that whileembodiments are described in reference to dual receiver systems,embodiments of the optical systems may be used in systems that includeone or more than two receivers.

Tables 1A through 6 provide example values for various optical andphysical parameters of the example embodiments of the optical systemsdescribed in reference to FIGS. 1 through 6. In the Tables, alldimensions are in millimeters (mm) unless otherwise specified. “S#”stands for surface number. A positive radius indicates that the centerof curvature is to the right (object side) of the surface. A negativeradius indicates that the center of curvature is to the left (imageside) of the surface. “Infinity” stands for infinity as used in optics.The thickness (or gap/separation) is the axial distance to the nextsurface.

In the example embodiments of the optical systems described in referenceto FIGS. 1 through 6, the lens elements may be formed of various plasticor glass materials. Two or more of the lens elements in a given opticalsystem may be formed of different materials. For the materials of thelens elements, a refractive index (e.g., N_(d) at the helium d-linewavelength) may be provided, as well as an Abbe number V_(d) (e.g.,relative to the d-line and the C- and F-lines of hydrogen). The Abbenumber, V_(d), may be defined by the equation:V _(d)=(N _(d)−1)/(N _(F) −N _(C)),where N_(F) and N_(C) are the refractive index values of the material atthe F and C lines of hydrogen, respectively.

Note that the values given in the following Tables for the variousparameters in the various embodiments of the optical systems are givenby way of example and are not intended to be limiting. For example, oneor more of the parameters for one or more of the surfaces of one or moreof the lens elements in the example embodiments, as well as parametersfor the materials of which the elements are composed, may be givendifferent values while still providing similar performance for theoptical systems. In particular, note that some values in the Tables maybe scaled up or down for larger or smaller implementations of theoptical systems as described herein.

Further note that surface numbers (S#) of the elements in the variousembodiments of the optical systems as shown in the Tables are listedfrom a first surface (FIGS. 1 and 2), stop (FIG. 4), or object-sidesurface of a first lens element (FIGS. 3, 5, and 6), to a last surfaceat the image plane/photosensor surface.

FIG. 1 and Tables 1A and 1B—Receiver Optical System 100

FIG. 1 and Tables 1A-1B illustrate an example embodiment 100 of anoptical system that may, for example, be used as a medium-range opticalsystem in LiDAR applications. Medium range receiver optics that may beused in LiDAR systems, for example a LiDAR system as described in FIGS.7A-7B and 8A-8B, are described. A fundamental advantage of embodimentsof a dual transmit and receive system for LiDAR is a realizablearchitecture that includes scanning mirrors, micro electro-mechanical(MEMs) mirrors, and single photon-avalanche detectors (SPADs) forcounting single photo-electron events from close to medium range (e.g.,50 meters or less) with acceptable manufacturing risk, eye safetymargin, and probability of photon detection. In some embodiments,receiver components of the LiDAR system may also incorporate embodimentsof the long-range and/or short-range receiver optical systems asdescribed herein.

In some embodiments, optical system 100 may have five refractive lenselements 101-105 arranged in order from a first lens element 101 on theobject side of optical system 100 to a last lens element 105 on theimage side of optical system 100. Optical system 100 may include a stop,for example located between lens 102 and lens 103 as shown in FIG. 1.Optical system 100 may also include an optical bandpass filter, forexample located at or on surface S13 of lens 104 as shown in FIG. 1.Optical system 100 may be configured to refract light from an objectfield to an image plane formed at or near the surface of a sensor 180.Sensor 180 may, for example, include one or more single photon-avalanchedetectors (SPADs). However, other types of photodetectors may be used insome embodiments.

A component of the medium-range receiver is a wide field optical design.In at least some embodiments, the medium-range receiver utilizes opticalfilters, scanning mirrors, and a nominal one-dimensional SPAD toincrease the probability of positive photon events.

Lens element 101 may be a meniscus lens with negative refractive power.In some embodiments, both surfaces of lens element 101 may be spherical.Lens element 101 may have a convex object side surface and a concaveimage side surface. In some embodiments, the object side surface of lenselement 101 may be spherical, and the image side surface of lens element101 may be even aspheric. In some embodiments, lens element 102 may be abiconvex lens with positive refractive power. Alternatively, lens 102may be a plano-convex or meniscus lens with positive refractive power.Lens element 102 may have a plano or near-plano (slightly convex orslightly concave) object side surface and a convex image side surface.In some embodiments, both surfaces of lens element 102 may be spherical.Lens element 103 may be a meniscus lens with positive refractive power.Lens element 103 may have a concave object side surface and a conveximage side surface. In some embodiments, both surfaces of lens element103 may be spherical. In some embodiments, the object side surface oflens element 103 may be even aspheric, and the image side surface oflens element 103 may be spherical. Lens element 104 may be aplano-convex lens with positive refractive power. Lens element 104 mayhave a convex object side surface and a plano image side surface. Insome embodiments, both surfaces of lens element 104 may be spherical.Lens element 105 may be a meniscus lens with negative refractive power.Lens element 105 may have a convex object side surface and a concaveimage side surface. In some embodiments, the object side surface of lenselement 105 may be spherical, and the image side surface of lens element105 may be even aspheric. In some embodiments, both surfaces of lenselement 105 may be spherical.

Properties and advantages of optical system 100 may include one or moreof, but are not limited to:

-   -   The optical system 100 may have five lenses.    -   The optical system 100 may be a single aspherical surface        design. In some embodiments, for example, optical system 100 has        a single aspherical surface on the last or image side surface        (S15 of lens 105), while the other lens surfaces are spherical        or plano.    -   The optical system 100 may include a stop (aperture), for        example located between lens 102 and lens 103 as illustrated in        FIG. 1.    -   The optical system 100 may have a medium entrance pupil (e.g.,        within a range of 10 to 15 mm, for example 12.7 mm) and may        provide a relatively small F-number (e.g., 1.6 or less). In some        embodiments, field of view of the medium-range optical system        may be between 15 degrees and 60 degrees.    -   The optical system 100 may include an optical band pass filter        for optimum probability of detection for photoelectric events.        For example, optical system 100 may include a filter at or on a        plano surface S13 of lens 104 as shown in FIG. 1 to mitigate the        likelihood of unwanted pupil ghosts at the focus.    -   The optical system 100 may be optimized for wide temperature        variation over a large temperature range (e.g., −40 degrees C.        to 80 degrees C.) and source bandwidth (e.g., 900 nm-1000 nm).    -   The optical system 100 may be optimized for compact SPAR        configurations.    -   The optical system 100 may be a telecentric lens (e.g., an        image-space telecentric lens) to minimize the effects of photon        centroid motion and triangulation for short optical ranges        and/or to ensure that the signal at the sensor is correctly        mapped from angle in the object space to placement in the image        space irrespective of object distance.    -   The optical system 100 may have less than 10% negative        distortion and at or about 90% relative illumination over the        field of view for optimum photon probability of detection.

TABLE 1A Optical system 100 Radius Thickness/ Diameter Element SurfaceSurface type (mm) Gap (mm) (mm) Mech. Diameter Object Standard InfinityInfinity 0 0 S1 Standard Infinity 9.474131 54.26515 54.26515 S2 StandardInfinity 0 43.32536 43.32536 S3 Standard Infinity 9.474131 43.3253643.32536 Lens S4 Standard 28.42043 3.508947 28.09618 31.09618 101 LensS5 Even 16.73604 6.942533 23.05080 31.09618 101 aspheric Lens S6Standard 412.3939 4.681104 21.16178 23.16178 102 Lens S7 Even −75.491916.40639 19.46264 23.16178 102 aspheric STOP Standard Infinity 0 13.9034313.90343 S9 Standard Infinity 20.99281 13.90343 13.90343 Lens S10 Even−40.71941 7.857838 31.43584 37.51835 103 aspheric Lens S11 Standard−26.90251 0.7661502 35.51835 37.51835 103 Lens S12 Standard 56.135677.484278 40.26053 42.26053 104 Lens S13 Standard Infinity 0.383597939.84414 42.26053 104 Lens S14 Standard 24.06883 16.70885 37.9369739.93697 105 Lens S15 Even 20.35999 9.267508 24.39245 39.93697 105aspheric Image Standard Infinity 21.78418 21.78418

TABLE 1B Optical system 100 Element Glass Chip zone Conic Lens 101 N-SF21.5 0 Lens 102 SF6 1 0 Lens 103 SF6 1 0 Lens 104 SF6 1 0 Lens 105N-LASF46A 1 0FIG. 2 and Table 2—Long-Range Optical System 200

FIG. 2 and Table 2 illustrate an example embodiment 200 of an opticalsystem that may, for example, be used as a long-range optical system inLiDAR applications. In some embodiments, optical system 200 may havefive refractive lens elements 201-205 arranged in order from a firstlens element 201 on the object side of optical system 200 to a last lenselement 205 on the image side of optical system 200. Optical system 200may include a stop, for example located between lens 202 and lens 203 asshown in FIG. 2. Optical system 200 may also include an optical bandpassfilter, for example located at or on surface S4 of lens 202 as shown inFIG. 2. Optical system 200 may be configured to refract light from anobject field to an image plane formed at or near the surface of a sensor290. Sensor 290 may, for example, include one or more singlephoton-avalanche detectors (SPADs). However, other types ofphotodetectors may be used in some embodiments.

Lens element 201 may be a biconvex lens with positive refractive power.In some embodiments, both surfaces of lens element 201 may be spherical.Lens element 202 may be a plano-concave lens with negative refractivepower. Lens element 202 may have a concave object side surface and aplano (flat) image side surface. In some embodiments, the object sidesurface of lens element 202 may be spherical. In some embodiments, theobject side surface of lens element 202 may contact the image sidesurface of lens 201. Lens element 203 may be a meniscus lens withpositive refractive power. Lens element 203 may have a convex objectside surface and a concave image side surface. In some embodiments, bothsurfaces of lens element 203 may be spherical. Lens element 204 may be ameniscus lens with positive refractive power. Lens element 204 may havea convex object side surface and a concave image side surface. In someembodiments, both surfaces of lens element 204 may be spherical. Lenselement 205 may be a biconcave lens with negative refractive power. Insome embodiments, both surfaces of lens element 205 may be spherical.

Properties and advantages of optical system 200 may include one or moreof, but are not limited to:

-   -   The optical system 200 may have five or fewer lenses.    -   One or more of the lenses may have spherical surfaces; in some        embodiments, all of the lenses have spherical surfaces.    -   The optical system 200 may have a large entrance pupil (e.g.,        40 mm) and a small F-number (e.g., 1.125 or less), and may        provide a small field of view (e.g., 15 degrees or less).    -   The optical system 200 may be a telecentric lens (e.g., an        image-space telecentric lens) to provide minimum image scale        change when a focal plane is introduced and during variations in        temperature.    -   The optical system 200 may include an optical bandpass filter        for optimum probability of detection for photoelectric events.        For example, the optical system 200 may include a filter at or        on surface S4 of lens 202 as shown in FIG. 2 to mitigate the        likelihood of unwanted pupil ghosts at the focus (image plane).    -   The optical system 200 may achieve system specifications over a        large temperature range (e.g., −40 degrees C. to 80 degrees C.)        and source bandwidth (e.g., 900 nanometers (nm)-1000 nm).    -   The optical system 200 may be optimized for compact SPAD        configurations.    -   The optical system 200 may have less than 0.2% negative        distortion and almost 100% relative illumination over the field        of view for optimum photon probability of detection.    -   The optical system 200 may include a stop (aperture), for        example located between lens 202 and lens 203 as illustrated in        FIG. 2.

In some embodiments, the optical system 200 may be integrated with amultiple scanning mirror system (e.g., a MEMS mirror) to collect laserradiation from long-range objects and image the objects with sufficientprecision to one or more SPAR chips at the focus (image plane).

TABLE 2 Receiver optical system 200 Radius of curvature Thickness Mate-Surface Type (mm) or Gap rial Object STANDARD Infinity Infinity S1STANDARD Infinity 25.40005 Lens 201 S2 STANDARD 50.52775 12.62115 BK7Lens 202 S3 STANDARD −47.35588 5.635905 SF6 S4 STANDARD Infinity0.6117068 Stop Stop STANDARD Infinity 2.391139 Lens 203 S6 STANDARD30.71983 10.29709 S-LAL9 S7 STANDARD 52.66062 20.62353 Lens 204 S8STANDARD 23.27457 6.938469 SF6 S9 STANDARD 166.2798 5.000918 Lens 205S10 STANDARD −27.73724 4.946685 SF6 S11 STANDARD 139.1987 5.0 Sensor 290Image STANDARD InfinityFIG. 3 and Table 3—Short-Range Optical System 300

FIG. 3 and Table 3 illustrate an example embodiment 300 of an opticalsystem that may, for example, be used as a short-range optical system inLiDAR applications. In some embodiments, optical system 300 may have sixrefractive lens elements 301-306 arranged in order from a first lenselement 301 on the object side of optical system 300 to a last lenselement 306 on the image side of optical system 300. Optical system 300may include a stop, for example located between lens 302 and lens 303 asshown in FIG. 3. Optical system 300 may also include an optical bandpassfilter, for example located at or on surface S12 of lens 304 as shown inFIG. 3. Optical system 300 may be configured to refract light from anobject field to an image plane formed at or near the surface of a sensor390. Sensor 390 may, for example, include one or more singlephoton-avalanche detectors (SPADs). However, other types ofphotodetectors may be used in some embodiments.

Lens element 301 may be a meniscus lens with negative refractive power.Lens element 301 may have a convex object side surface and a concaveimage side surface. In some embodiments, surface S4 of lens element 301may be even aspheric or spherical, and surface S5 of lens element 301may be spherical. Lens element 302 may be a biconvex lens with positiverefractive power. In some embodiments, surface S6 of lens element 302may be spherical, and surface S7 of lens element 302 may be evenaspheric or spherical. Lens element 303 may be a meniscus lens withpositive refractive power. Lens element 303 may have a concave objectside surface and a convex image side surface. In some embodiments,surfaces S10 and S11 of lens element 303 may be spherical. Lens element304 may be a plano-convex lens with positive refractive power. Lenselement 304 may have a plano (flat) object side surface and a conveximage side surface. In some embodiments, surface S13 of lens 304 may bespherical. Lens element 305 may be a meniscus lens with negativerefractive power. In some embodiments, surface S14 of lens element 305may be convex, and surface S15 of lens element 305 may be concave. Insome embodiments, surface S14 of lens element 305 may be spherical, andsurface S15 of lens element 305 may be even aspheric or spherical. Lenselement 306 may be a biconvex lens with positive refractive power. Insome embodiments, surface S16 of lens element 306 may be spherical, andsurface S17 of lens element 306 may be even aspheric or spherical.

Properties and advantages of optical system 300 may include one or moreof, but are not limited to:

-   -   The optical system 300 may have six or fewer lenses.    -   One or more of the lenses may have spherical surfaces; in some        embodiments, all of the lenses have spherical surfaces.    -   The optical system 300 may have a small F-number (e.g., 2.0 or        less), and may provide a large field-of-view (e.g., 60 degrees        or greater).    -   The optical system 300 may be a telecentric lens (e.g., an        image-space telecentric lens) to minimize the effects of photon        centroid motion and triangulation for short optical ranges.    -   The optical system 300 may include an optical bandpass filter        for optimum probability of detection for photoelectric events.        For example, the optical system 300 may include a filter at or        on a flat surface S12 of lens 304 as shown in FIG. 3.    -   The optical system 300 may be optimized for wide temperature        variation over a large temperature range (e.g., −40 degrees C.        to 80 degrees C.) and source bandwidth (e.g., 900 nm-1000 nm).    -   The optical system 300 may be optimized for compact SPAD        configurations.    -   The optical system 300 may have less than 5% negative distortion        and greater than 60% relative illumination over the field for        optimum photon probability of detection.    -   The optical system 300 may include a stop (aperture), for        example located between lens 302 and lens 303 as illustrated in        FIG. 3.

In some embodiments, the optical system 300 may be integrated with amultiple scanning mirror system (e.g., a MEMS mirror) to collect laserradiation from short-range objects and image the objects with sufficientprecision to one or more SPAD chips at the focus (image plane).

TABLE 3 Receiver optical system 300 Radius of Thickness Mate- SurfaceType curvature or Gap rial Lens 301 S4 Even Aspheric 160.0949 2.0 BK7 S5STANDARD 9.310111 1.705925 Lens 302 S6 STANDARD 44.142 3.000001 SF6 S7Even Aspheric −20.31882 0.1999999 Stop STANDARD Infinity 0 Lens 303 S9STANDARD Infinity 4.144555 S10 STANDARD −8.87866 5.0 SF6 S11 STANDARD−10.73887 0.4619624 Lens 304 S12 STANDARD Infinity 5.017804 SF6 S13STANDARD −23.29207 0.6136292 Lens 305 S14 STANDARD 21.1782 6.056791 SF6S15 Even Aspheric 11.76076 5.193445 Lens 306 S16 STANDARD 19.427514.478419 SF6 S17 Even Aspheric −120.8147 7.127467 Sensor 390 ImageSTANDARD InfinityFIG. 4 and Table 4—Receiver Optical System 400

FIG. 4 and Table 4 illustrate an example embodiment 400 of an opticalsystem that may, for example, be used as a short-range optical system inLiDAR applications. In some embodiments, optical system 400 may haveseven refractive lens elements 401-407 arranged in order from a firstlens element 401 on the object side of optical system 400 to a last lenselement 407 on the image side of optical system 400. Optical system 400may include a stop, for example located between lens 401 and the objectfield as shown in FIG. 4. Optical system 400 may also include an opticalbandpass filter 410, for example located between lens 404 and 405 asshown in FIG. 4, or alternatively may have an optical bandpass filtercoating on surface S9 of lens 404 as shown in FIG. 4. Optical system 400may be configured to refract light from an object field to an imageplane formed at or near the surface of a sensor 490. Sensor 490 may, forexample, include one or more single photon-avalanche detectors (SPADs).However, other types of photodetectors may be used in some embodiments.

Lens element 401 may be a meniscus lens with negative refractive power.Lens element 401 may have a concave object side surface and a conveximage side surface. In some embodiments, both surfaces of lens element401 may be spherical. Lens element 402 may be a meniscus lens withpositive refractive power. In some embodiments, both surfaces of lenselement 402 may be spherical. Lens element 402 may have a concave objectside surface and a convex image side surface. Lens element 403 may be aplano-convex lens with positive refractive power. Lens element 403 mayhave a plano (flat) object side surface and a convex image side surface.In some embodiments, the image side surface of lens element 403 may bespherical. Lens element 404 may be a plano-convex lens with positiverefractive power. Lens element 404 may have a convex object side surfaceand a plano (flat) image side surface. In some embodiments, the objectside surface of lens 404 may be spherical. Lens element 405 may be abiconvex lens with positive refractive power. In some embodiments, bothsurfaces of lens element 405 may be spherical. Lens element 406 may be abiconcave lens with negative refractive power. In some embodiments, bothsurfaces of lens element 206 may be spherical. In some embodiments, theobject side surface of lens element 406 may contact the image sidesurface of lens 405. Lens element 407 may be a meniscus lens withpositive refractive power. In some embodiments, both surfaces of lenselement 407 may be spherical. Lens element 702 may have a convex objectside surface and a concave image side surface.

Properties and advantages of optical system 400 may include one or moreof, but are not limited to:

-   -   The optical system 400 may be a fast lens with a low F-number,        for example within a range of 1.5 to 1.6, for example 1.53.    -   The optical system 400 may provide 45 degree field of view        coverage in both azimuth and elevation.    -   The optical system 400 may be corrected over a wide spectral        range to account for source wavelength variability (unit to        unit). For example, in some embodiments, up to +/−50 nm can be        tolerated with a simple refocus of the optical system 400 during        assembly.    -   The optical system 400 may be corrected for up to 12 nm spectral        width to accommodate the source spectral width and the drift of        the source spectrum with temperature.    -   The optical system 400 may include seven lens elements. In some        embodiments all of the lens elements have spherical surfaces,        which may lower costs.    -   The optical system 400 design allows for easy manufacturing        tolerances for the lens elements as well as for lens assembly.    -   The optical system 400 may be athermalized over a temperature        range of −40 degrees C. to 80 degrees C. when assembled with a        stainless steel barrel. This may, for example, help to ensure        the resolution of the system 400 over a wide operating range        while preserving both the focus and the focal length of the        system 400.    -   The optical system 400 may have a low distortion design that        allows pre-mapping of object angle to sensor position without        losing angular resolution.    -   The optical system 400 may be a telecentric lens (e.g., an        image-space telecentric lens) to ensure that the signal at the        sensor is correctly mapped from angle in the object space to        placement in the image space irrespective of object distance.    -   In some embodiments, a plano (flat) surface (e.g., surface S9 of        lens 404 as shown in FIG. 4) is available internal to the        optical system 400 in a space that is collimated or nearly        collimated to allow the deposition of a narrow pass band coating        directly on the plano surface of the lens (e.g., surface S9 of        lens 404 as shown in FIG. 4), thus obviating the need for a        filter element. Alternatively, in some embodiments, a separate        filter 410 may be placed in the same collimated space (between        lens 404 and lens 405), and performance can be recovered by a        simple refocus during assembly.    -   The optical system 400 may include a stop (aperture), for        example at or in front of lens 401 as illustrated in FIG. 4.

In some embodiments, the optical system 400 may be integrated with amultiple scanning mirror system (e.g., a MEMS mirror) to collect laserradiation from short-range objects and image the objects with sufficientprecision to one or more SPAR chips at the focus (image plane).

TABLE 4 Receiver optical system 400 Radius of Thickness Surfacecurvature or Gap Refractive Element Surface type (mm) (mm) Index AbbeNumber Object Infinity Infinity Stop S1 Stop Infinity 19.90 Lens 401 S2Spherical −27.52 10.75 1.784701 26.08 S3 Spherical −289.00 1.7 Lens 402S4 Spherical −165.66 8.00 1.804200 46.50 S5 Spherical −45.74 1.00 Lens403 S6 Spherical Infinity 7.50 1.804200 46.50 S7 Spherical −79.90 1.00Lens 404 S8 Spherical 76.20 8.84 1.753930 52.27 S9 Plano Infinity 1.00Filter S10 Plano Infinity 2.00 1.516800 64.17 (optional) S11 PlanoInfinity 1.00 Lens 405 S12 Spherical 43.70 15.00 1.743972 44.85 Lens 406S13 Spherical −162.65 8.50 1.805182 25.43 S14 Spherical 26.16 8.013 Lens407 S15 Spherical 53.00 15.00 1.696800 55.41 S16 Spherical 261.0010.687262 Sensor 490 Sensor Plano Infinity 0.00FIG. 5 and Table 5—Receiver Optical System 500

FIG. 5 and Table 5 illustrate an example embodiment 500 of an opticalsystem that may, for example, be used as a long-range optical system inLiDAR applications. In some embodiments, optical system 500 may havefive refractive lens elements 501-505 arranged in order from a firstlens element 501 on the object side of optical system 500 to a last lenselement 505 on the image side of optical system 500. Optical system 500may include a stop, for example located between lens 501 and lens 502 asshown in FIG. 5. Optical system 500 may also include an optical bandpassfilter, for example located at or on the image side surface (surface S2)of lens 501 as shown in FIG. 5. Optical system 500 may be configured torefract light from an object field to an image plane formed at or nearthe surface of a sensor 590. Sensor 590 may, for example, include one ormore single photon-avalanche detectors (SPADs). However, other types ofphotodetectors may be used in some embodiments.

Lens element 501 may be a plano-convex lens with positive refractivepower. Lens element 501 may have a convex object side surface and aplano (flat) image side surface. In some embodiments, the object sidesurface of lens element 501 may be spherical. Lens element 502 may be ameniscus lens with positive refractive power. Lens element 502 may havea convex object side surface and a concave image side surface. In someembodiments, both surfaces of lens element 502 may be spherical. Lenselement 503 may be a biconcave lens with negative refractive power. Insome embodiments, both surfaces of lens element 503 may be spherical.Lens element 504 may be a biconvex lens with positive refractive power.In some embodiments, both surfaces of lens element 504 may be spherical.Lens element 505 may be a meniscus lens with positive refractive power.In some embodiments, both surfaces of lens element 505 may be spherical.Lens element 505 may have a convex object side surface and a concaveimage side surface.

Properties and advantages of optical system 500 may include one or moreof, but are not limited to:

-   -   The optical system 500 may be a fast lens with a low F-number,        for example within a range of 1.1 to 1.2, for example 1.125.    -   The optical system 500 may provide a 10 degree field of view.    -   The optical system 500 may be corrected over a wide spectral        range to account for source wavelength variability (unit to        unit). For example, in some embodiments, up to +/−50 nm can be        tolerated with a simple refocus of the optical system 500 during        assembly.    -   The optical system 500 may be corrected for up to 12 nm spectral        width to accommodate the source spectral width and the drift of        the source spectrum with temperature.    -   The optical system 500 may include five lens elements. In some        embodiments all of the lens elements have spherical surfaces,        which may lower costs.    -   The optical system 500 design allows for easy manufacturing        tolerances for the lens elements as well as for lens assembly.    -   The optical system 500 may be athermalized over a temperature        range of −40 degrees C. to 80 degrees C. when assembled with a        stainless steel barrel. This may, for example, help to ensure        the resolution of the system 500 over a wide operating range        while preserving both the focus and the focal length of the        system 500.    -   The optical system 500 may have a low distortion design (e.g.,        distortion<−0.2%).    -   The optical system 500 may be a telecentric lens (e.g., an        image-space telecentric lens) to ensure that the signal at the        sensor is correctly mapped from angle in the object space to        placement in image space irrespective of object distance.    -   In some embodiments, a plano surface (e.g., surface S2 of lens        element 501 in FIG. 5) is available internal to the optical        system 500 in a space that is collimated or nearly collimated to        allow the deposition of a narrow pass band coating directly on        the plano surface of the lens (e.g., surface S2 of lens element        501 in FIG. 5), thus obviating the need for a filter element.    -   The optical system 500 may include a stop (aperture), for        example located between lens 501 and lens 502 as illustrated in        FIG. 5.

In some embodiments, the optical system 500 may be integrated with amultiple scanning mirror system (e.g., a MEMS mirror) to collect laserradiation from long-range objects and image the objects with sufficientprecision to one or more SPAR chips at the focus (image plane).

TABLE 5 Receiver optical system 500 Radius of Thickness Surfacecurvature or Gap Refractive Element Surface type (mm) (mm) Index AbbeNumber Object Infinity Infinity Lens 501 S1 Spherical 65.700 6.4001.743972 44.85 S2 Plano Infinity 0.000 Stop S3 Stop Infinity 9.144 Lens502 S4 Spherical 36.000 8.000 1.717360 29.62 S5 Spherical 89.650 6.120Lens 503 S6 Spherical −209.900 8.000 1.487490 70.41 S7 Spherical 23.00019.167 Lens 504 S8 Spherical 48.300 5.000 1.805180 25.36 S9 Spherical−81.240 1.002 Lens 505 S10 Spherical 16.500 8.000 1.805180 25.36 S11Spherical 13.500 4.168 Sensor 590 Sensor Plano Infinity 0.000FIG. 6 and Table 6—Receiver Optical System 600

FIG. 6 and Table 6 illustrate an example embodiment 600 of an opticalsystem that may, for example, be used as a short-range optical system inLiDAR applications. In some embodiments, optical system 600 may have sixrefractive lens elements 601-606 arranged in order from a first lenselement 601 on the object side of optical system 600 to a last lenselement 606 on the image side of optical system 600. Optical system 600may include a stop, for example located between lens 602 and lens 603 asshown in FIG. 6. Optical system 600 may also include an optical bandpassfilter, for example located at or on surface S13 of lens 606 as shown inFIG. 6. Optical system 600 may be configured to refract light from anobject field to an image plane formed at or near the surface of a sensor690. Sensor 690 may, for example, include one or more singlephoton-avalanche detectors (SPADs). However, other types ofphotodetectors may be used in some embodiments.

Lens element 601 may be a meniscus lens with positive refractive power.Lens element 601 may have a concave object side surface and a conveximage side surface. In some embodiments, both surfaces of lens element601 may be spherical. Lens element 602 may be a meniscus lens withnegative refractive power. Lens element 602 may have a convex objectside surface and a concave image side surface. In some embodiments, bothsurfaces of lens element 602 may be spherical. Lens element 603 may be ameniscus lens with positive refractive power. Lens element 603 may havea concave object side surface and a convex image side surface. In someembodiments, both surfaces of lens element 603 may be spherical. Lenselement 604 may be a biconvex lens with positive refractive power. Insome embodiments, both surfaces of lens 604 may be spherical. Lenselement 605 may be a meniscus lens with negative refractive power. Insome embodiments, the object side surface of lens element 605 may beconvex, and the image side surface of lens element 605 may be concave.In some embodiments, both surfaces of lens element 605 may be spherical.Lens element 606 may be a plano-convex lens with positive refractivepower. Lens element 606 may have a convex object side surface and aplano (flat) image side surface. In some embodiments, the object sidesurface of lens element 606 may be spherical.

Properties and advantages of optical system 600 may include one or moreof, but are not limited to:

-   -   The optical system 600 may provide moderately fast optics (e.g.        F-number of 2.0) in a compact form.    -   The optical system 600 may provide a 60 degree field of view.    -   The optical system 600 may be corrected over a wide spectral        range to account for source wavelength variability (unit to        unit). For example, in some embodiments, up to +/−50 nm can be        tolerated with a simple refocus of the optical system 600 during        assembly.    -   The optical system 600 may be corrected for up to 12 nm spectral        width to accommodate the source spectral width and the drift of        the source spectrum with temperature.    -   The optical system 600 may include six lens elements. In some        embodiments all of the lens elements have spherical surfaces,        which may lower costs.    -   The optical system 600 design allows for easy manufacturing        tolerances for the lens elements as well as for lens assembly.    -   The optical system 600 may be athermalized over a temperature        range of −40 degrees C. to 80 degrees C. when assembled with a        stainless steel barrel. This may, for example, help to ensure        the resolution of the system 600 over a wide operating range        while preserving both the focus and the focal length of the        system 600.    -   The optical system 600 may have a low distortion design that        allows pre-mapping of object angle to sensor position without        losing angular resolution.    -   The optical system 600 may be a telecentric lens (e.g., an        image-space telecentric lens) to ensure that the signal at the        sensor is correctly mapped from angle in the object space to        placement in image space irrespective of object distance.    -   In some embodiments, a plano surface (e.g., surface S13 of lens        element 606 in FIG. 6) is available internal to the optical        system 600 in a space with a low diversity of angles to allow        the deposition of a narrow pass band coating directly on the        plano surface of the lens (e.g., surface S13 of lens element 606        in FIG. 6), thus obviating the need for a filter element.    -   The optical system 600 may include a stop (aperture), for        example located between lens 602 and lens 603 as illustrated in        FIG. 6.

In some embodiments, the optical system 400 may be integrated with amultiple scanning mirror system (e.g., a MEMS mirror) to collect laserradiation from short-range objects and image the objects with sufficientprecision to one or more SPAR chips at the focus (image plane).

TABLE 6 Optical system 600 Radius of Thickness Surface curvature or GapRefractive Element Surface type (mm) (mm) Index Abbe Number ObjectInfinity Infinity Lens 601 S1 Spherical −380.00 2.65 1.805180 25.36 S2Spherical −112.90 5.40 Lens 602 S3 Spherical 19.20 5.40 1.487490 70.41S4 Spherical 6.95 5.96 Stop S5 Plano Infinity 9.40 Lens 603 S6 Spherical−23.33 3.60 1.805180 25.36 S7 Spherical −14.40 1.00 Lens 604 S8Spherical 127.00 3.70 1.805180 25.36 S9 Spherical −40.16 1.00 Lens 605S10 Spherical 17.93 6.00 1.805180 25.36 S11 Spherical 13.243 2.681 Lens606 S12 Spherical 24.41 6.00 1.805180 25.36 S13 Plano Infinity 9.853431Sensor 690 Sensor Plano Infinity 0.000Example LiDAR System

FIGS. 7A-7B and 8A-8B illustrate an example LiDAR system in whichembodiments of the optical systems as described in FIGS. 1 through 6 maybe implemented.

FIGS. 7A and 7B are logical block diagrams of an example LiDAR systemthat combines laser pulse transmissions in light ranging and detecting(LiDAR), and in which embodiments of the optical systems as illustratedin FIGS. 1 through 6 may be implemented, according to some embodiments.In FIG. 7A, LiDAR 1000 illustrates the combined transmission of twodifferent pulses, outbound pulse 1042 and 1044 via a common optical path1030. LiDAR 1000 may implement two laser transmitters 1012 and 1014.Each laser transmitter 1012 and 1014 may be configured to transmit aseparate train of one or more laser pulses (the reflections of which maybe captured to determine distance measurements). The type of laserpulses transmitted by the transmitters 1012 and 1014 may be the same ordifferent. For example transmitter 1012 may transmit a laser pulse witha same or different wavelength, pulse width, or amplitude than a laserpulse transmitted by transmitter 1014. In addition the different typesof laser pulses transmitted by transmitters 1012 and 1014, the timing oftransmitting the laser pulses may be different. For example, in someembodiments, laser pulses from transmitter 1012 may be transmittedaccording to one pulse repetition rate (PRR) (e.g., 1 megahertz),whereas laser pulses from transmitter 1014 may be transmitted accordingto an increased or decreased PRR (e.g., 0.5 megahertz or 1.5 megahertz).In some embodiments, transmissions between the two transmitters may alsobe interleaved according to a transmission timing difference (i.e.,delta) between the two laser transmitters.

LiDAR 1000 may also implement a common optical path 1030 which combinespulses 1032 sent from the two different transmitters, transmitters 1012and 1014. For example, as illustrated in FIG. 7A, outbound pulse 1042may be a pulse transmitted from transmitter 1012 and outbound pulse 1044may be a pulse transmitted from transmitter 1014 which are sent via thesame optical path, common optical path 1030. Different combinations ofoptical devices (e.g., lenses, beam splitters, folding mirrors, or anyother device that processes or analyzes light waves) may be implementedas part of common optical path 1030 to combine pulses from transmitter1012 and 1014 which may be transmitted with orthogonal polarizations(e.g., two different linear polarization states). For instance, laserpulses sent from transmitter 1012 may have vertical polarization stateand laser pulses sent from transmitter 1014 may have a horizontalpolarization state. To combine the pulses of orthogonal polarizationstates, the various combinations of optical devices in common opticalpath 1030 may be implemented to ensure that polarization states of thetwo different laser pulses are distinguishable, both on transmission andreflection, in various embodiments. In this way, reflections of thedifferent pulses received via common optical path 1030 may be separated1034 (as illustrated in FIG. 7B) and directed to the appropriatereceiver for calculating a distance measure particular to the pulsetransmitted from a particular transmitter (e.g., pulse 1042 transmittedfrom transmitter 1012 may be matched with the detection of inbound pulsereflection 1052 at receiver 1022, and outbound pulse 1044 may be matchedwith the detection of inbound pulse reflection 1054 at receiver 1024).FIGS. 8A-8B, discussed below, provide different examples of commonoptical paths which may be implemented.

As trains of laser pulses transmitted from transmitter 1012 and 1014 maybe combined and transmitted via common optical path 1030 the distancemeasures which can be captured by LiDAR 1000 may vary. For instance, asthe transmission delta between pulses may be configurable, the densityor location distance measurements provided by LiDAR 1000 may be changedaccordingly. Similarly, the PRR for transmitter 1012 may be slower tocover longer ranges. In some scenarios, transmitter 1012 may beconfigured to provide long range distance measures and transmitter 1014may be configured to provide close range distance measures, effectivelyproviding a larger range of distance measures (e.g., dynamic range) thatmay be determined by LiDAR 1000. For example, transmitter 1012 may sendlaser pulses with a 1550 nm wavelength for long range distance measuresand transmitter 1014 may send laser pulses with a 930 nm wavelength tocapture a close in range of distance measures. In some embodiments,receiver 1022 may include a long range receiver optical system asdescribed herein to receive return light from transmitter 1012, andreceiver 1024 may include a short range receiver optical system asdescribed herein to receive return light from transmitter 1014.

In some embodiments, a transmitter and receiver may be included in LIDAR1000 that are configured to provide medium range distance measures inplace of the long range transmitter/receiver or the short rangetransmitter/receiver, or in addition to the long and short rangetransmitters and receivers. For example, a medium-range transmitter maysend laser pulses in the range between the long 1550 nm wavelength andthe short 930 nm wavelength to capture a medium range of distancemeasures. In some embodiments, the medium-range receiver may include amedium range receiver optical system as described herein in relation toFIG. 1 to receive return light from the medium-range transmitter.

As noted above, different optical devices may be implemented to combineand separate laser pulses sent from different laser transmitters so thatcorresponding reflections are directed to the appropriate receivers.FIGS. 8A and 8B illustrate an example optical path for laser pulses andpulse reflections, according to some embodiments. In FIG. 8A, theoutbound pulse path (1470 and 1472) for two different laser transmitters(1410 and 1412) is illustrated. Optics 1400 may implement transmitter1410 which may send a laser pulse in a linear polarization state to beamsplitter 1434 which in turn may direct the pulse to polarizing beamsplitter 1430. Polarizing beam splitter 1430 may direct the pulsethrough quarter wave plate 1440, which may transform the polarizationstate from a linear polarization state to a circular polarization state.The transformed pulse may then be reflected off scanning mirror 1460 outinto the environment. Optics 1400 may implement transmitter 1412 whichmay send a laser pulse to beam splitter 1432. The laser pulse sent fromtransmitter 1412 may be in a linear polarization state orthogonal thepolarization state of pulses sent from transmitter 1410. Beam splitter1432 may direct the pulse to polarizing beam splitter 1430. Polarizingbeam splitter 1430 may direct the pulse through quarter wave plate 1440,which may transform the polarization state from a linear polarizationstate to a circular polarization state. The transformed pulse may thenbe reflected off scanning mirror 1460 which may direct the pulse outinto the environment.

In FIG. 8B, pulse reflection path 1480 (which corresponds to reflectionsof pulses transmitted according to outbound pulse path 1470) and pulsereflection path 1482 (which corresponds to reflections of pulsestransmitted according to outbound pulse path 1472) are illustrated. Apulse reflection of a pulse transmitted by transmitter 1410 may bereceived and reflected off scanning mirror 1460, directing the pulsethrough quarter-wave plate 1440. As the pulse was transmitted into theenvironment in a circular polarization state, the reflection may also bein a circular polarization state that is the reverse of the circularpolarization state transmitted. For example, if outbound path 1470transmits laser pulses in right-handed circular polarization state, thecorresponding reflections will be received in left-handed circularpolarization state. Thus, when quarter-wave plate 1440 transforms thepolarization of the reflection the resulting linear polarization isorthogonal to the linear polarization state in which the laser pulse wasoriginally transmitted from transmitter 1410. Thus, polarizing beamsplitter 1430 directs the pulse through beam splitter 1432 and receiverlens 1452 in order to reach and be detected by receiver 1422. A pulsereflection of a pulse transmitted by transmitter 1412 may be receivedand reflected off scanning mirror 1460, directing the pulse throughquarter-wave plate 1440. Again, the reflection may also be in a circularpolarization state that is the reverse of the circular polarizationstate transmitted. For example, if outbound path 1472 transmits laserpulses in left-handed circular polarization state, the correspondingreflections will be received in right-handed circular polarizationstate. Thus, when quarter-wave plate 1440 transforms the polarization ofthe reflection the resulting linear polarization is orthogonal to thelinear polarization state in which the laser pulse was originallytransmitted from transmitter 1412. Thus, the pulse passes throughpolarizing beam splitter 1430, beam splitter 1434, and receiver lens1450 in order to reach and be detected by receiver 1420.

In some embodiments, receiver 1420/lens 1450 may include a long rangereceiver optical system as described herein to receive return light fromtransmitter 1412, and receiver 1422/lens 1452 may include a short rangereceiver optical system as described herein to receive return light fromtransmitter 1410. In some embodiments, the systems of FIGS. 8A and 8Bmay instead or also include medium range transmitter and receivercomponents and a medium range receiver optical system, for example asillustrated in FIG. 1, to receive return light from the medium rangetransmitter. For example, in some embodiments, receiver 1420/lens 1450may include a long-range receiver optical system as described herein toreceive return light from a long-range transmitter 1412, and receiver1422/lens 1452 may include a medium-range receiver optical system asdescribed herein to receive return light from a medium-range transmitter1410. As another example, in some embodiments, receiver 1420/lens 1450may include a medium-range receiver optical system as described hereinto receive return light from a medium-range transmitter 1412, andreceiver 1422/lens 1452 may include a short-range receiver opticalsystem as described herein to receive return light from a short-rangetransmitter 1410.

FIG. 9 is a high-level flowchart of a method of operation for a remotesensing system that includes light transmitters and receivers and acommon optical path; the receivers may include optical systems asillustrated in FIGS. 1 through 6. The method of FIG. 9 may, for example,be implemented in a LiDAR system as illustrated in FIGS. 7A-7B and8A-8B.

As indicated at 2000, transmitters (e.g., two laser transmitters) emitlight to a common optical path, for example as illustrated in FIGS. 7Aand 8A. In some embodiments, laser pulses from one transmitter may betransmitted according to one pulse repetition rate (PRR), whereas laserpulses from the other transmitter may be transmitted according to adifferent PRR. In some embodiments, the transmitters may send laserpulses with different wavelengths. For example, one transmitter may sendlaser pulses with a 1550 nm wavelength for long range of distancemeasures, and the other transmitter may send laser pulses with a 930 nmwavelength to capture a close in range of distance measures. As anotherexample, one transmitter may send laser pulses in the range between thelong 1550 nm wavelength and the short 930 nm wavelength to capture amedium range of distance measures, and the other transmitter may sendlaser pulses with a 930 nm wavelength to capture a close in range ofdistance measures. As another example, one transmitter may send laserpulses in the range between the long 1550 nm wavelength and the short930 nm wavelength to capture a medium range of distance measures, andthe other transmitter may send laser pulses with a 1550 nm wavelength tocapture long range distance measures. Note that these examples are notintended to be limiting.

As indicated at 2010, the light is directed by the common optical pathto an object field. In some embodiments, as illustrated in FIG. 8A, eachtransmitter may send a laser pulse in a linear polarization state torespective beam splitters, which in turn may direct the pulses to apolarizing beam splitter. In some embodiments, the linear polarizationstate of one transmitter may be orthogonal to the linear polarizationstate of the other transmitter. The polarizing beam splitter may directthe pulses through a quarter wave plate, which may transform thepolarization state from a linear polarization state to a circularpolarization state. The transformed pulses may then be reflected by ascanning mirror (e.g., a MEMS mirror) into the environment (i.e., theobject field). The light (pulses) may be reflected by surfaces orobjects in the object field. At least some of the reflected light mayreturn to and be captured by the LiDAR system.

As indicated at 2020, reflected light from the object field may bedirected by the common optical path to respective receivers. The commonoptical path may be configured to direct light that was emitted by oneof the transmitters to one receiver (e.g., a medium-range receiver), andto direct light that was emitted by the other transmitter to the otherreceiver (e.g., a short- or long-range receiver), for example asillustrated in FIG. 8B. In some embodiments, the reflected light fromeach transmitter may be in a circular polarization state that is thereverse of the circular polarization state that was transmitted. Forexample, if the light from one transmitter was transmitted in aleft-handed circular polarization state, the corresponding reflectionswill be received in a right-handed circular polarization state. When thequarter-wave plate transforms the polarization of the reflected light,the resulting linear polarization is orthogonal to the linearpolarization state in which the laser pulse was originally transmittedfrom a respective transmitter. The reflected light from each transmitterthen passes through or is directed by the beam splitters in the opticalpath to reach the receiver corresponding to the transmitter.

As indicated at 2030, optical systems of the respective receiversrefract the light to respective photodetectors or sensors, for exampleone or more one-dimensional single photon-avalanche detectors (SPADs).An example optical system that may be used in a medium-range receiver isillustrated in FIG. 1. Example optical systems that may be used in along-range receiver are illustrated in FIGS. 2 and 5. Example opticalsystems that may be used in a short-range receiver are illustrated inFIGS. 3, 4, and 6.

As indicated at 2040, light captured at the photodetectors may beanalyzed, for example to determine range information for objects orsurfaces in the environment. In some embodiments, light captured by along-range receiver may be analyzed to determine ranges for long-rangeobjects or surfaces (e.g., 20 meters to 200 meters), light captured by amedium-range receiver may be analyzed to determine ranges for close- tomedium-range objects or surfaces (e.g., 50 meters or less), and lightcaptured by a short-range receiver may be analyzed to determine rangesfor short-range objects (e.g., 20 meters or less). For example,distances may be calculated based on the difference between a time atwhich a laser pulse transmission is sent and a time at which areflection of the laser pulse transmission is received. The analysis ofthe reflected light received at and captured by the different receiversmay be used in many different applications. For instance, multipledistance measures taken over an area can be processed to generate a highresolution map, which can be used in a variety of differentapplications, including, but not limited to, geological surveys,atmospheric measurements, object detection, autonomous navigation, orother remote environmental sensing applications.

The arrow returning from element 2040 to element 2000 indicates that themethod may continuously emit light (e.g., laser pulses) and receive andprocess reflections of the light as long as the system (e.g., LiDARsystem) is in use.

Although specific embodiments have been described above, theseembodiments are not intended to limit the scope of the presentdisclosure, even where only a single embodiment is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The scope of the present disclosure includesany feature or combination of features disclosed herein (eitherexplicitly or implicitly), or any generalization thereof, whether or notit mitigates any or all of the problems addressed herein. Accordingly,new claims may be formulated during prosecution of this application (oran application claiming priority thereto) to any such combination offeatures. In particular, with reference to the appended claims, featuresfrom dependent claims may be combined with those of the independentclaims and features from respective independent claims may be combinedin any appropriate manner and not merely in the specific combinationsenumerated in the appended claims.

Various ones of the methods described herein may be implemented insoftware, hardware, or a combination thereof, in different embodiments.In addition, the order of the blocks of the methods may be changed, andvarious elements may be added, reordered, combined, omitted, modified,etc. Various modifications and changes may be made as would be obviousto a person skilled in the art having the benefit of this disclosure.The various embodiments described herein are meant to be illustrativeand not limiting. Many variations, modifications, additions, andimprovements are possible. Boundaries between various components andoperations are somewhat arbitrary, and particular operations areillustrated in the context of specific illustrative configurations.Other allocations of functionality are envisioned and may fall withinthe scope of claims that follow. Finally, structures and functionalitypresented as discrete components in the exemplary configurations may beimplemented as a combined structure or component. These and othervariations, modifications, additions, and improvements may fall withinthe scope of embodiments as defined in the claims that follow.

What is claimed is:
 1. A remote sensing system, comprising: twotransmitters that transmit light through a common optical path to anobject field; and two receivers that detect reflections of thetransmitted light received at the system through the common opticalpath, wherein the two receivers include a medium-range receivercomprising a medium-range optical system including a plurality ofrefractive lens elements that refract a portion of the light reflectedfrom a range of 50 meters or less to a first sensor that captures thelight, wherein field of view of the medium-range optical system isbetween 15 and 60 degrees, and wherein F-number of the medium-rangeoptical system is 1.6 or less.
 2. The remote sensing system as recitedin claim 1, wherein the medium-range optical system has an entrancepupil within a range of 10 to 15 millimeters.
 3. The remote sensingsystem as recited in claim 1, wherein the medium-range optical systemincludes five refractive lens elements, and wherein surfaces of the lenselements in the medium-range optical system include one or more ofspherical, even-aspheric, or flat/plano surfaces.
 4. The remote sensingsystem as recited in claim 3, wherein the five refractive lens elementsinclude, in order from an object side of the medium-range optical systemto an image side of the medium-range optical system: a first lenselement with negative refractive power; a second lens element withpositive refractive power; a third lens element with positive refractivepower; a fourth lens element with positive refractive power; and a fifthlens element with negative refractive power.
 5. The remote sensingsystem as recited in claim 4, wherein the first lens element is ameniscus lens with a convex object side surface and a concave image sidesurface; wherein the third lens element is a meniscus lens with aconcave object side surface and a convex image side surface; wherein thefourth lens element is a plano-convex lens; and wherein the fifth lenselement is a meniscus lens with a convex object side surface and aconcave image side surface.
 6. The remote sensing system as recited inclaim 4, wherein the medium-range optical system further includes: astop located between the second lens element and the third lens element;and an optical bandpass filter located at or on an image side surface ofthe fourth lens element.
 7. The remote sensing system as recited inclaim 3, wherein the five refractive lens elements include, in orderfrom an object side of the medium-range optical system to an image sideof the medium-range optical system: a first lens element, wherein thefirst lens element is a meniscus lens with negative refractive power; asecond lens element, wherein the first lens element is a biconvex lenswith positive refractive power; a third lens element, wherein the thirdlens element is a meniscus lens with positive refractive power; a fourthlens element, wherein the fourth lens element is a plano-convex lenswith positive refractive power; and a fifth lens element, wherein thefifth lens element is a meniscus lens with negative refractive power. 8.The remote sensing system as recited in claim 7, wherein themedium-range optical system further comprises: a stop located betweenthe second lens element and the third lens element; and an opticalbandpass filter located at the image side surface of the fourth lenselement.
 9. The remote sensing system as recited in claim 7, wherein themedium-range optical system is an image-space telecentric lens.
 10. Theremote sensing system as recited in claim 3, wherein the medium-rangeoptical system has an entrance pupil within a range of 10 to 15millimeters.
 11. The remote sensing system as recited in claim 1,wherein the medium-range optical system is an image-space telecentriclens.
 12. The remote sensing system as recited in claim 1, wherein thetwo receivers further include a short-range receiver comprising ashort-range optical system including a plurality of refractive lenselements that refract a portion of the light reflected from a range of20 meters or less to a second sensor that captures the light, whereinfield of view of the short-range optical system is between 45 and 65degrees, and wherein F-number of the short-range optical system is 2.0or less.
 13. The remote sensing system as recited in claim 1, whereinthe two receivers further include a long-range receiver comprising along-range optical system including a plurality of refractive lenselements that refract a portion of the light reflected from a range of20 meters or more to a second sensor that captures the light, whereinfield of view of the long-range optical system is 15 degrees or less,and wherein F-number of the long-range optical system is 1.2 or less.14. The remote sensing system as recited in claim 1, wherein the firstsensor includes one or more single photon-avalanche detectors.
 15. Amethod, comprising: emitting, by first and second transmitters of aremote sensing system, light to a common optical path of the remotesensing system; directing, by the common optical path, the light emittedby the first and second transmitters to an object field; receiving, atthe remote sensing system, a portion of the light reflected from theobject field; directing, by the common optical path, portions of thereceived light to first and second receivers of the remote sensingsystem, wherein light emitted by the first transmitter is directed tothe first receiver, and wherein light emitted by the second transmitteris directed to the second receiver; and refracting, by optical systemsof the first and second receivers, the light received at the respectivereceivers to photodetectors of the first and second receivers; whereinthe optical system of the first receiver includes a plurality ofrefractive lens elements that refract a portion of the light reflectedfrom a range of 50 meters or less to the photodetector of the firstreceiver, wherein field of view of the optical system of the firstreceiver is between 15 degrees and 60 degrees, and wherein F-number ofthe optical system of the first receiver is 1.6 or less.
 16. The methodas recited in claim 15, wherein the optical system of the secondreceiver includes a plurality of refractive lens elements that refract aportion of the light reflected from a range of 20 meters or less to thephotodetector of the second receiver, wherein field of view of theoptical system of the second receiver is between 45 and 65 degrees, andwherein F-number of the optical system of the second receiver is 2.0 orless.
 17. The method as recited in claim 15, wherein the optical systemof the second receiver includes a plurality of refractive lens elementsthat refract a portion of the light reflected from a range of 20 metersor more to the photodetector of the second receiver, wherein field ofview of the optical system of the second receiver is 15 degrees or less,and wherein F-number of the optical system of the second receiver is 1.2or less.
 18. The method as recited in claim 15, wherein the opticalsystem of the first receiver includes, in order from an object side ofthe optical system to an image side of the optical system: a first lenselement with negative refractive power; a second lens element withpositive refractive power; an aperture stop; a third lens element withpositive refractive power; a fourth lens element with positiverefractive power; an optical bandpass filter; and a fifth lens elementwith negative refractive power.
 19. The method as recited in claim 18,wherein an entrance pupil of the aperture stop is within a range of 10to 15 millimeters.